This invention involves automatic paper folding apparatus and more specifically an improvement device and method for the scoring of paper, prior to the folding operation.
Once a brochure is printed, it is usually necessary to fold the brochure at least in half and generally in thirds, quarter or whatever is designed. Mechanized automatic folding machines have been constructed and are available commercially. These machines utilize variable sheet gap control and stepless speed regulators to achieve optimum production. Buckle folding is accomplished by feeding a sheet between a series of rollers and specifically to a buckle mounth at a slight angle against a stop. Guide bars prevent the sheet from moving up or down and the sheet has only one possibility of getting out a designated area requiring it to buckle toward folding rollers which, as they rotate in an opposite direction draw it between the rollers. This action forms the fold. Before entering a buckle folding apparatus, for many types of paper stack, particularly the coated papers, it is necessary to score the paper so that it will buckle along a chosen line in a neat uncracked fashion. This scoring or creasing is a standard and required step in any buckle folding apparatus for many papers. Combination folds can be made and the rate of production in sheets per hour is dependent upon the running speed of the device. The running speed typically varies from about 45 to 150 meters per minute according to the paper stability. Taking into account the space between separate sheets, that being the distance between the rear edge and the leading edge of the following sheet, it is possible to run about 10,000 to 20,000 sheets per hour, depending upon the size of the sheet.
The term "scoring" is the common term used to describe placing an indent in the paper to facilitate and essentially assure folding along the proper line. However, the term "creasing" is somtime used for this operation, although that generally refers to an operation after the scoring has been completed. Typically, creasing devices are mounted on a pair of rotating parallel shafts, that are rotating in opposite directions with the paper drawn between the shafts from the side where the shafts are rotating toward each other. On one of the shafts is mounted a cylindrical member with a slot into the surface of the member in a circular shape around the cylinder. This scoring slot receives a male scoring member in the shape of a ring extending outwardly from a second cylindrical member mounted on the other rotating shaft such that the scoring member is aligned with the scoring slot. When the paper is pulled between the two rotating shafts, the paper is scored between the scoring member and the scoring slot. The scoring member is essentially an upraised rib formed as an integral part of the cylindrical member. Most importantly, both of the cylindrical members, one having the scoring slot and one having the scoring member, are both detachably, but firmly fixed to the rotating shafts so that each rotate at the same speed of the rotating shafts.
Different types of papers present different problems than the scoring operation. For some papers, the scoring apparatus tends to nick the edges of the paper as it initially grabs the paper between the scoring member and the scoring slot. Also with certain types of paper, a poor quality fold is obtained. This is particularly true of coated papers wherein the coating sometimes tends to crack during the folding operation unless a separate die press scoring device is used. For those paper, a separate operation on a separate machine greatly reduces the rate of processing. It is most desirable to be able to score and fold in the same machine. But that is not possible with some types of papers in the present equipment. The prior art devices do not satisfy these problems nor attain the objects described herein below.